Phase change memory (PCM) is a non-volatile memory commonly used in re-writable data storage media such as CDs and DVDs. The phenomenon relies on the ability of chalcogenide materials to exhibit unlimited and reversible phase change between their amorphous and crystalline phases, with each of these phases having very distinct optical and electrical properties. In electronic devices, each of these states is associated with one bit (0 or 1), which enables the storage of data.
The chalcogenide elements include sulfur, selenium, and tellurium. The chalcogenide materials used for PCM may take the form of an alloy and may include germanium and/or antimony. More particularly, Ge2Sb2Te5 (GST) is one of the most studied chalcogenide materials.
Chalcogenide materials may be deposited using sputter techniques. However, sputter techniques may not allow deposition of films of sufficient quality upon introduction of further scaling to tens of nanometers of 3D circuit. Chemical vapor deposition (CVD) and atomic layer deposition (ALD) of chalcogenide materials may be needed to allow the manufacturing of giga-bit devices.
The synthesis of (Me3Si)3SiTeSiMe3 and HTeSi(SiMe3)3 is reported, as well as the potential use of these compounds as CVD materials [P. J. Bonasia et al., New reagents for the synthesis of compounds containing metal-tellurium bonds: sterically hindered silyltellurolate derivatives and the X-ray crystal structures of [(THF)2LiTeSi(SiMe3)3]2 and [(12-crown-4)2Li][TeSi(SiMe3)3], J. Am. Chem. Soc. (1992) 114, pp. 5209-5214].
Becker et al. report TMS3Si—Te—Me and TMS3Si—Te—Te—SiTMS3. Synthese, Struktur and Reaktivitat des Lithium-[tris-trimethylsilyl]silyl]tellanids—DME, Z. Anorg Allg. Chem. (1992) 613, pp. 7-18.
Breunig reports the syntheses and properties of stibino or bismuthino selenides or tellurides, such as MeSb(SeMe)2. Phosphorus and Sulfur, 1988, Vol. 38, pp. 97-102.
The problem the industry faces is finding precursors of germanium, antimony, tellurium, selenium, or sulfur which have enough similarities (volatility, decomposition temperature, reaction kinetics . . . ) to allow their use for deposition of chalcogenide-containing films, especially in thermal ALD mode. A plasma source is sometimes added to address this issue, but the radical species generated tend to damage the substrate and step coverage is usually insufficient.